Well, I guess they don't get my jokes either, so it's only fair

Katie: Knock knock.
Max: Who's there?
Katie: Quesadilla.
Max: Quesadilla who?
Katie: Quesdilla guy!
(Hysterical laughter from both children.)

Katie: Knock knock.
Max: Who's there?
Katie: Bucket.
Max: Bucket who?
Katie: Bucket full of eggs lady!
(Cue laughter again.)